Optical subtraction of images in real time

J. Grinberg*, E. Marom

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


A subtraction scheme capable of handling in real time two incoherently illuminated scenes and providing the sign of the subtracted information is described. The scheme utilizes two Hughes Liquid Crystal Light Valves, onto which the two images to be subtracted are projected. One valve is analyzed in between crossed polarizers, while the other one is in between parallel polarizers, both polarizers being implemented with a polarizing beam splitter and a quarter wave plate. The common output image plane onto which both images are superimposed, displays an intensity proportional to the difference between the two inputs. This intensity "rides" on a constant background intensity thus displaying the difference signal as well as its polarity. The read-in and read-out beams could be coherent as well as incoherent, the latter being more desirable due to its speckle-free image. Experimental results obtained with incoherent illumination will be shown.

Original languageEnglish
Pages (from-to)66-74
Number of pages9
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - 8 Dec 1977
Externally publishedYes


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